The nematode fauna of Plummers Island, on the Potomac River near Washington, D.C., is virtually unknown. Only three species have been reported from the Island: Daptonema dubium (Bütschli, 1873) Lorenzen, 1977, Isolaimium papillatum Cobb, 1920, and Tylolaimophorus cylindricum (Cobb, 1920) Goodey, 1963. We surveyed terrestrial and aquatic habitats on Plummers Island to begin to characterize its nematode fauna. Nematodes of 47 genera were found, representing 9 orders and 32 families, including an estimated 59 species. We provide diagnoses of the 3 species reported from the literature, a classified list of genera, their habitats and life stages found, and an estimate of the number of species found in each genus.